Two paddle-steamers - "Apostol Pavel" and her nearly identical sister "Apostol Pyotr" were built in England in 1906 for Imperial Russia to be operated on Lake Ladoga and Gulf of Finland as cargo-passenger ships.
During WWI both were mobilized as shallow draft minesweepers "TSch-18" and "TSch-19". After the war followed by Russian Revolution of 1917 the vessels ended up in Finland where they got named "Pavel" and "Peeter" and were offered for sale as passenger ships. However there were no buyers and the ships were rusting moored in Helsinki.
In 1920 Estonia, whose territorial waters were still infested with mines from WWI, bought both vessels as minesweepers. They got new names: "Ristna" and "Suurop" and were clearing fairways for one year. After that Estonian government tried to use them as cargo-passenger ships but they couldn't compete with private transportation companies and yet again got moored for a few years; this time in Tallinn.
In 1927 the ships were converted to minelayers carrying 175 mines each. "Suurop" was armed with Vickers Mk.2 40mm gun while "Ristna" got only a couple of searchlights. Estonia ordered two 40mm Bofors guns from Sweden but they were not delivered until 1940. The same year Estonia was included into Soviet Union; soon after that all her ships were transferred to Soviet Navy. "Ristna" was in service as training minelayer till 1957 when she was scrapped for metal. "Suurop" sunk after hitting a German mine in 1941.